1. Field of the Invention
The present invention relates to a rotary actuator composed of an electric motor and a speed reduction device.
2. Description of Related Art
An example of a rotary actuator composed of an electric motor and a speed reduction device, both disposed in contact with each other in its axial direction, is disclosed in JP-A-2005-282601. In order to improve an output torque of this kind of rotary actuator without enlarging its size, it is conceived to reduce a thickness of a stator core in a radial direction while increasing the number of winding in stator coils and/or to use materials having a higher grade in a rotor and a stator in the electric motor.
However, it is difficult to increase the output torque by reducing the radial thickness of the stator and increasing the number of winding in the stator coils because a magnetic flux in the stator core becomes saturated. A manufacturing cost of the rotary actuator becomes high if materials having a higher grade are used.